[Python] How can I put two NumPy arrays into a matrix with two columns?

I am trying to put two NumPy arrays into a matrix or horizontally stack them. Each array is 76 elements long, and I want the ending matrix to have 76 rows and 2 columns. I basically have a velocity/frequency model and want to have two columns with corresponding frequency/velocity values in each row.

Here is my code ('f' is frequency and 'v' the velocity values, previously already defined):

print(f.shape)
print(v.shape)
print(type(f))
print(type(v))
x = np.concatenate((f, v), axis = 1)


This returns

(76,)
(76,)
<class 'numpy.ndarray'>
<class 'numpy.ndarray'>


And an error about the concatenate line that says:

AxisError: axis 1 is out of bounds for array of dimension 1


I've also tried hstack except for concatenate, as well as vstack and transposing .T, and have the same error. I've also tried using Pandas, but I need to use NumPy, because when I save it into a txt/dat file, Pandas gives me an extra column with numbering that I do not need to have.

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